ryan's challenge? to be seen as credible and keep romney's momentum going. in most battleground states, the race is essentially tied, and obama's lead in ohio appears to be narrowing. ryan has only previously participated in around eight debates for his congressional seat. the vice president has run for president twice, debating 16 times, plus squaring off against sarah palin for the gig he has now. >> can i call you joe? >> reporter: biden has been cramming, studying ryan's positions and the book, "young guns," the book that the congressman co-wrote, looking for fodder. >> i just want to make sure when i say these things that i don't have the congressman saying, "no, no, no, i don't have that position." >> reporter: though he is known for gaffes and verbosity, the structure of the debates seems to help him, forcing him to be concise and stick to script. >> he's fast on the cuff. he's a witty guy. he knows who he is and he's been doing this for 40 years. >> reporter: in addition to watching clips of the vice president's many debates, ryan has studied news cl